Some cameras, conventionally referred to as three-dimensional (3D) cameras, image a scene to determine distances to features in the scene. Such cameras may use infrared (IR) light to image the scene. For example, a gated time of flight (TOF) 3D camera, may transmit a train of IR light pulses to illuminate a scene and shutter or “gate on” a photosensor in the camera for a short exposure period following each transmitted light pulse. Light reflected from the transmitted light pulses that reaches the photosensor during the exposure periods is registered by pixels in the photosensor. Distance to a feature in the scene imaged on a pixel of the photosensor is determined as a function of an amount of reflected light incident on the pixel during the exposure periods.
To identify distances to features in the scene with the features, it is generally advantageous to acquire a conventional contrast image (“picture image”) of the scene with visible light incident on pixels of a photosurface that are in known correspondence with pixels of the photosensor that provides the IR image of the scene. In some TOF 3D cameras, the IR and visible light images of a scene are acquired by two separate photosensors that are aligned so that corresponding pixels in the two photosensors image the same feature of the scene
In some TOF 3D cameras, the IR image is acquired by IR sensitive pixels in a photosensor on which a scene is imaged and the visible light picture is acquired by different, optionally red (R), green (G), and blue (B) sensitive pixels in the same photosensor.